mk: make it completely generic

commands now fed from a file, include/common.sh
which in turn also includes other lib files

this makes mk completely generic, and means
that changes will now be completely in sync
with cbmk, ensuring a lack of merge conflicts,
though the file was already pretty small anyway.

Signed-off-by: Leah Rowe <leah@libreboot.org>

include/common.sh

@@ -0,0 +1,19 @@
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+. "include/lib.sh"
+. "include/init.sh"
+. "include/vendor.sh"
+. "include/mrc.sh"
+. "include/inject.sh"
+. "include/rom.sh"
+. "include/release.sh"
+. "include/get.sh"
+. "include/chromebook.sh"
+
+xbcommands=" \
+version \
+release \
+download \
+inject \
+prep_mr_import \
+"